By providing the major source of inhibitory circuitry in the cerebral cortex, GABAergic neurons are required for the synchronous activity necessary to generate sustained oscillations among neurons within a network that are essential during perception, coordinated movement, learning and memory. Cortical deficits in inhibitory neuronal transmission have been implicated in neuropsychiatric disorders such as epilepsy, autism, and schizophrenia. Generating a limitless supply of GABAergic neurons from would allow for the extensive use of these cells in a variety of disease models in order to evaluate their potential for use in cell based therapies. The goal of this proposal is to generate cortical GABAergic interneurons from mouse embryonic stem (ES) cells. Using modifications of published protocols, I will first optimize the production of telencephalic (FoxG1+) progenitors that co-express Nkx2.1, a transcription factor that is required for the specification of major subgroups of cortical interneurons in rodents. Since Nkx2.1 also gives rise to other populations of subcortically generated cells, I have generated an ES cell line that expresses green fluorescent protein under control of the promoter region of Lhx6, a transcription factor whose expression is enriched within Nkx2.1-lineage interneuron precursors and maintained in most of these cells through postnatal development. Using this and other tools, I will direct ES cells towards putative interneuron progenitor (mitotic) or precursor (postmitotic, but not yet migrated into cortex) states and test their capacity to migrate, survive, and differentiate within postnatal mouse cortex. These experiments could have important implications for cell based therapies for medication resistant chronic focal epilepsy. In addition, successful derivation of Nkx2.1-lineage interneuron's from ES cells would provide an invaluable system for the study of intrinsic and extrinsic factors regulating the development of these critical neurons.